i think that's how everybody does that around here.
i mean there's this new speedy's add it says something about wireless modem and 3k connection at 70 AR$ but i think it comes with a 6/8 month contract or something like that, so yeah the best you can do it's buy a wireless router by yourself and connect the modem to it, then you just have to mannage your router settings, and that's all.
i think Galerias Jardin (in Florida St.) is the best place to get a good one.
And in the meanwhile you can get free wi-fi connection at starbucks, aroma or tons of coffee stores.